The subject matter of this invention is culture tube racks, and more particularly a culture tube rack to facilitate the preparation and growth of aerobic and anaerobic agar slant tube cultures, and liquid slant tube cultures.
Agar slant culture tubes are used in growing, storing, and testing of both aerobic and anaerobic organisms. The aerobic organisms are exposed on the surface and typically require a surface area of exposure to air. Conversely, the anaerobic organisms are disposed throughout the medium and should not have a surface exposure to air. The various desired distributions of culture media can be obtained by the angular positioning or tilt of the rack.
Agar medium is purchased in powder form for mixing with hot water. The medium is then placed in a culture tube and sterilized. While the medium is hot, it remains liquid. If a rack full of tubes is removed from a sterilizer and placed on its side, the medium will cool and solidify to a consistency of gelatin in a position slanted relative to the axis of the tube. This solidified sterile culture is then inoculated as desired with organisms.
Typically, agar slant culture tubes are prepared using standard tube racks by leaning them against some other object during cooling and solidifying. Such practice is necessarily inconvenient and furthermore the angle of the culture slant is estimated and therefore variable from one rack to the next.
This situation has been addressed in the prior art. One result is a rack having an angularly adjustible cradle. Another is a rack having a fixed 5.degree. tilt angle with springs to hold the test tubes in place. Another is a rack having a protruding lip on which to rest the rack in an inclined position.
It is an object of the present invention to provide a culture tube rack which is adapted for holding culture tubes vertically, for holding them at a first angle from the horizontal as for aerobic cultures, for holding them at a second angle from the horizontal as for growing anaerobic cultures, and for convenient stacking of rack upon rack. It is also intended that the rack be used for holding and growing cultures, in the two slant positions, in a liquid medium.
The present invention is practiced in one form by a culture tube rack having end plates, with front edges extending upwardly and outwardly at 20.degree. from the vertical, and rear edges extending upwardly and outwardly at 5.degree. from the vertical, so that the rack can be positioned upright or at 5.degree. or 20.degree. slants for setting of media and growth of agar cultures. The end plates are furthermore configured for vertical nesting of one rack atop another.